Video encoding technology enables efficient transmission of digital video. Some real-time video streaming applications, such as video conferencing, are particularly demanding because user experience depends on efficient and robust encoding techniques for minimal delay and adequate image quality. Wireless channels as a platform for video transmission further constrain encoding technology because the underlying networks often have very dynamic channel bandwidth.
The number of bits required for encoding each video frame is referred to as the encoding rate and is often not constant throughout a video sequence. Rate control is implemented at the video encoder to guarantee successful decoding and displaying of the video data streamed into the decoder. Video codecs have adjustable compression parameters to increase or decrease the encoding rates in order to accommodate the different transmission bandwidths of the various types of channels.
Provisions for Scalable Video Coding (SVC) are included in Annex G extension of the H.264/MPEG-4 Part 10 Advanced Video Codec (AVC) video compression standard. The H.264 standard has been prepared by the Joint Video Team (JVT), which includes ITU-T SG16 Q.6, also known as VCEG (Video Coding Expert Group), and of the ISO-IEC JTC1/SC29/WG11 (2003), known as MPEG (Motion Picture Expert Group). SVC standardizes the encoding of a video bit stream that also contains one or more subset bit stream requiring less bandwidth. The subset bit streams may support different spatial resolutions (screen sizes), different temporal resolutions (frame rates), or different quality (SNR) video signals.
SVC technology may be useful in real-time video streaming applications as a means of dealing with variations in encoder bitrate budget. Within the SVC standard there is considerable latitude for implementations that may offer a superior video streaming service as there is a complex relationship between video quality and the quantity of the data needed to represent the video (i.e., bitrate). In general, the higher the bitrate, the more accurate is the spatial frequency spectrum approximation of an encoder. Yet, higher accuracy may not necessary yield higher perceived quality for the human viewer.